We have notched every piglet that was ever born here. Personally I don't see how you can keep good records without doing this. For us when we were raising both crosses & pure breds of three breeds we started each breed off at Litter 1. Clear as mud right?! Hah! The first litter of Large Blacks born here were Litter #1 as were the first litter of GOS & the cross breeds. This ensured that we were not getting too high in litter numbers/ear notches too soon. As it was obvious which breed was which there was no question of one getting muddled.
With the ear notches done which does not hurt the pigs despite what some folks say, we then could write down in our records what each one was. That way if one died we knew exactly which one it was. Ear notching within the first 24 hours is the best time to do it. Mama is still feeling tired. Grab the piglet & hold it's mouth shut, do the notching & replace quickly. Make sure mama had been given a good bowl of goodies away from the nest.
Liz